The queen, who produces the most complex pheromone known in the animal
world, has at her command a cache of chemicals to make other bees do her
bidding. She uses this powerful and seductive perfume to attract a retinue
of worker bees that lick and groom her and carry chemical signals back
to the rest of the hive.

Worker bees rub their antennae on the queen's abdomen, where some of the chemicals are released. Photo by C.I. Keeling.

Four new chemicals in the pheromone have been identified, revealing that
it is more complex than imagined. The four chemicals enhance a core group
of five chemicals that had been previously identified.

“We were very surprised to find these four new chemicals,”
says Christopher Keeling, who led the study at Simon Fraser University
in British Columbia, Canada. Together, these nine chemicals are called
the queen retinue pheromone.

In the study, the researchers discovered that genetics plays a role in
how bees respond to the pheromone. The scientists selectively bred bees
that would respond to certain groups of chemicals in the pheromone.

The queen exudes these chemicals from a number of glands in different
parts of the body such as the head and abdomen. It is rare for a pheromone
associated with one behavior to come from several glands.

“Not only is the pheromone a blend of multiple chemicals, but the
blend comes from different sources,” says Gene Robinson of the University
of Illinois at Urbana-Champaign, who has spearheaded the project to sequence
the bee genome, now underway at Baylor College of Medicine in Houston,
Texas. Robinson was not involved in the study.

Clockwise from top-left. 1. A retinue of workers surrounds their queen. 2. Queen's abdomen. 3. Bees lick and rub their antennae on a glass lure with a synthetic pheromone as if the lure was their own queen. 4. Petri dish and bees, with glass lure at 6'oclock. All photos by C.I. Keeling.

For social insects like bees and ants, pheromones are the main form of
communication. Bees have become models for studying social behavior in
animals, including the genetics behind social traits.

To identify the new components, the researchers tested various chemicals
on “a queen bee lure.” They coated a glass pipette with chemicals
to mimic the queen bee’s perfume and waited to see whether the bees
would come calling. The experiment was conducted 26,000 times with the
lures.